The thermal obliteration of dysrhythmia sites in the surface of the cardiac muscle has proved successful in the treatment of cardiac dysrhythmias, particularly disorders caused by endomyocardial tissue. An ablation catheter was inserted in a controlled manner into the patient's heart and a local coagulation was performed using an essentially point electrode in the surface of the muscle, i.e. in the area of the tissue responsible for the conduction system. In doing so, a coagulation scar down to a depth of 3 to 5 mm was usually generated by a high-frequency generator with frequencies of 300 kHz to 700 kHz. This method does, however, suffer from the drawback that in order to carry out treatment, the ablation catheter must be re-placed several times in the area of the treatment site and that in consequence, the treatment process is time-consuming and labor-intensive.